1. Field of the Invention
The present invention relates to a passive type electroluminescence (EL) display apparatus in which anodes and cathodes, each pair of which having an emissive layer therebetween, are arranged in a matrix.
2. Description of Related Art
Organic EL devices are ideal for thin display configurations as they emit light and can eliminate need for a backlight as required in liquid crystal displays, and because they have unlimited viewing angle. Thus, wide application of organic EL devices is expected in the next generation of display devices.
As shown in an example in FIG. 1, an organic EL device (hereinafter referred to as an xe2x80x9cOEL devicexe2x80x9d) 1 can be constituted by forming an anode 3 comprising a transparent electrode made of ITO (Indium Tin Oxide) or the like on a transparent glass substrate 2, and forming, between the anode 3 and a cathode 4 comprising an MgIn alloy, a hole-transport layer 5 comprising MTDATA (4,4xe2x80x2,4xe2x80x3-tris(3-methylphenylphenylamino)tryphenylamine), an emissive layer 6 comprising TPD (N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-di(3-methylphenyl)-1,1xe2x80x2-biphenyl-4,4xe2x80x2-diamine) and Rubrene, and an electron-transport layer 7 comprising Alq3 (quinolinol aluminum complex) which are accumulated in this order. Holes injected from the anode 3 and electrons injected from the cathode 4 are recombined within the emissive layer 6 to emit light, which is radiated outward from the transparent anode side in the direction shown in the figure.
Display apparatuses employing thus configured OEL devices for each of a plurality of pixels disposed in a matrix and driving each OEL device for each pixel can be divided into two types according to their structure for driving each OEL device: passive type, and active type using TFTs. The circuit structure of the passive type is schematically shown in FIG. 2.
As shown in FIG. 2, individual matrices 8 and 9 are provided for the upper half and the lower half of a display screen, respectively. In the matrices 8 and 9, of the pair of electrodes in the aforementioned EL devices, the anodes 3 are column electrodes while the cathodes 4 are row electrodes. Each row electrode 4 is formed to intersect with all the column electrodes in each matrix. The column electrodes 3u in the matrix 8 extend in the column direction in the upper half of the screen (display area) so as to serve as common electrode lines for each pixel in the column direction, while the column electrodes 3d in the matrix 9 extend in the column direction in the lower half of the screen so as to serve as common electrode lines for each pixel in the column direction.
For the matrices 8 and 9, first and second column drivers 10, 11 for supplying column driving signals and first and second row drivers 12, 13 for supplying row driving signals as scan signals, are provided.
Of the scan signals supplied from the first and second row drivers 12 and 13, the scan signal of only the selected row of a plurality of rows becomes a low level for two horizontal scan periods (2H) while the scan signals for the other rows become a high level. Meanwhile, the first and second column drivers 10 and 11, to which gray-scale data mDATA for expressing the display gray scale of each pixel are input, output pulse signals having pulse widths proportional to this gray-scale data as column driving signals. The column driving signals are at a high level during the pulse width period, and thus, the EL device of the row that inputs the low level scan signal emits light.
Typically, the gray-scale data are temporarily stored in frame memories 14, 15 each having a capacity corresponding to one screen (one frame), and data stored in the upper half in one frame memory are sequentially supplied, line by line, into the first column driver 10, whereas the data in the lower half are sequentially supplied, line by line, into the second column driver 11. The first and second row drivers 12 and 13 scan each line at the same time in a sequence from top to bottom, so that display is achieved simultaneously in both of the divided halves of the screen.
If only one frame memory is provided, there is a possibility that the lower half of the screen displays data from the previous frame while the upper half displays data from a new frame which is already rewritten, resulting in different frame displays between the upper and lower screens. In order to avoid such a disadvantage, the two frame memories 14 and 15 are provided. Namely, while data are being read from one frame memory, data corresponding to the next frame is written into the other frame memory, and alternate repetition of this process will enable normal display.
The conventional passive type EL display apparatus which drives the devices in the divided manner as described above requires, as essential elements, frame memories for temporarily storing data in order to achieve normal display, and this enlarges the circuit scale entailing a cost increase in spite of the simple structure of the display section.
The present invention was made to solve the aforementioned problem of the related art, and aims to provide a light emitting display apparatus, for example an organic electroluminescence display apparatus such as an EL apparatus, capable of executing normal display without increasing the circuit scale.
In accordance with one aspect of the present invention, there is provided a light emitting display apparatus comprising display pixels that emit light arranged in a matrix, wherein each display pixel includes an emissive layer between first and second electrodes, said first electrodes being constituted by a column electrode extending in a column direction and said second electrodes being constituted by a row electrode extending in a row direction, each display pixel is formed at a point where said column electrode and said row electrode intersect, and said column electrode includes a first column electrode corresponding to display pixels at odd rows of display pixels associated as one column and a second column electrode corresponding to display pixels at even rows of said display pixels associated as the same one column. Said first and second column electrodes are driven independently, and display pixels at adjacent odd and even rows are simultaneously driven by row electrodes which are individually corresponded thereto.
In accordance with another aspect of the present invention, there is provided an electroluminescence display apparatus, wherein an emissive layer is disposed between an anode and a cathode, said anode being designated for a column electrode and said cathode being designated for a row electrode, said column electrode and said row electrode being arranged so as to intersect with each other, and wherein each display pixel is formed at a point where said column electrode and said row electrode intersect, said column electrode is divided into a first column electrode corresponding to display pixels at odd rows and a second column electrode corresponding to display pixels at even rows, said first and second column electrodes are individually driven by respective first and second column driver circuits, and said row electrode is driven by a row driver circuit, such that row electrodes at an odd row and at an even row which are adjacent in the column direction are driven simultaneously.
In accordance with another aspect of the present invention, in an apparatus as described above, during alternating first and second periods, said first column driver circuit receives data to be displayed on the display pixels at odd rows during a first period and said second column driver circuit receives data to be displayed on the display pixels at even rows during a second period, and said first and second column driver circuits and said row driver circuit output signals for driving the corresponding display pixels during a period corresponding to said first and second periods or during the first and second periods following said first and second periods when said data are received.
As described above, by simultaneously driving the adjacent display pixels at odd and even rows, within the column driver circuits, display data can be supplied in a line by line sequence to each display pixel in the display region more reliably than in the apparatus having frame memories corresponding to two screens, in which display data of one frame memory are displayed in the display region in a divided drive manner for the upper and lower section of the screen. Thus, the display data can be supplied in sequence to each display pixel of the display region without using a frame memory. Therefore, the circuit scale for the passive type emissive display apparatus is decreased to thereby reduce apparatus cost.
In accordance with still another aspect of the present invention, there is provided a light emitting display apparatus comprising display pixels that emit light arranged in a matrix, wherein each display pixel includes an emissive layer between first and second electrodes, said first electrodes being constituted by a column electrode extending in a column direction and said second electrodes being constituted by a row electrode extending in a row direction, each display pixel is formed at a point where said column electrode and said row electrode intersect, said column electrode includes a first column electrode corresponding to display pixels at odd rows of display pixels associated as one column and a second column electrode corresponding to display pixels at even rows of said display pixels associated as the same column, said first and second column electrodes being driven independently, said row electrode functions as a common row electrode for the display pixels at odd and even rows which are adjacent in the column direction, such that the common row electrode simultaneously drives said display pixels at adjacent odd and even rows.
In accordance with another aspect of the present invention, there is provided an electroluminescence display apparatus, wherein an emissive layer is disposed between an anode and a cathode, said anode being designated for a column electrode and said cathode being designated for a row electrode, said column electrode and said row electrode being arranged so as to intersect with each other, each display pixel is formed at a point where said column electrode and said row electrode intersect, said column electrode is divided into a first column electrode corresponding to display pixels at odd rows and a second column electrode corresponding to display pixels at even rows, said first and second column electrodes are individually driven by respective first and second column driver circuits, and said row electrode functions as a common row electrode for the display pixels at adjacent odd and even rows in the column direction, said common row electrode being driven by a row driver circuit to simultaneously drive the display pixels at odd and even rows.
In accordance with another aspect of the present invention, in an apparatus as described above, during alternating first and second periods, said first column driver circuit receives data to be displayed on display pixels at odd rows during a first period and said second column driver circuit receives data to be displayed on display pixels at even rows during a second period, and said first and second column driver circuits and said row driver circuit output signals for driving the corresponding display pixels during a period corresponding to said first and second periods or during the first and second periods following said first and second periods when said data are received.
The display pixels at odd and even rows which are adjacent in the column direction are driven by the same common row electrode, such that the number of outputs in the row driver circuit for driving the row electrodes is halved compared to that when the row electrodes are formed for each row, to thereby reduce the scale of said row driver circuit. Thus, elimination of the frame memory along with the reduction in the circuit scale of the row driver circuit results in a lower cost of the driver circuit while maintaining high display quality of the display apparatus.
In accordance with still another aspect of the present invention, there is provided a light emitting display apparatus having display pixels, each including an emissive layer between first and second electrodes, arranged in a matrix, comprising row electrodes extending in a row direction to form a striped pattern; and column electrodes extending in a column direction to form a striped pattern, wherein each of said display pixels is formed at a point where a row electrode and a column electrode intersect such that these electrodes respectively constitute said first and second electrodes, said column electrodes are constituted by comb-shaped first column electrodes whose teeth form said first and second electrodes of the display pixels at odd rows and comb-shaped second column electrodes whose teeth form said first and second electrodes of the display pixels at even rows which associated with the same column as said display pixels at odd rows, and the display pixels at adjacent odd and even rows in the column direction are driven simultaneously.
In accordance with still another aspect of the present invention, in an apparatus described above, two of said row electrode for respectively supplying row signals to said display pixels at adjacent odd and even rows are driven simultaneously.
In accordance with yet still another aspect of the present invention, in an apparatus described above, the display pixels at adjacent odd and even rows are driven simultaneously by a common row electrode for said display pixels.
By forming the first and second column electrodes in a comb shape as describe above, two of said column electrode for alternately driving the display pixels at odd and even rows associated as one column can be effectively disposed on a substrate. Further, in the display apparatus thus configured, the display data can be supplied to each display pixel in the display region in a line by line sequence within the column driver circuits more reliably than in the apparatus having frame memories corresponding to two screens, in which the display data of one frame memory are displayed in the display region in a divided drive manner for the upper and lower section of the screen, and a driving circuit having a small scale can be achieved.
Further, according to the present invention, in any of the above described apparatuses, the emissive layer may comprise an organic compound with light emitting function.
The emissive layer using such an organic compound is very advantageous in color display apparatuses or the like due to large variety of emissive colors and the wide range of materials.